A TFT (Thin Film Transistor) is also known as a thin film field effect transistor. A TFT-LCD (Thin Film Transistor Liquid Crystal Display) is also known as a thin film field effect transistor liquid crystal display. Each pixel on this type of liquid crystal display is driven by the thin film transistor integrated therebehind, which has a high response speed, high brightness, high contrast, small size, low power consumption, no radiation, etc., and dominates in the current display market.
The main structure of a TFT-LCD includes a TFT array substrate, a color film substrate, and a liquid crystal layer filled between these two substrates. In the conventional TFT-LCD technology, generally, the bottom gate structure of the array substrate is used. The on-state current on the array substrate of this type of TFT-LCD is proportional to the channel width W, and inversely proportional to the channel length L. The magnitude of the on-state current substantially depends on the size of the width-length ratio of the channel, W/L. Under the conventional processing manner, the channel length L of the TFT is mostly equivalent to the distance between the source electrode and the drain electrode, generally at least 4-5 um. Increasing the channel width W will sacrifice the aperture ratio to a certain extent, so that the on-state current in the TFT cannot be too high, and the display effect of the TFT-LCD is limited. Therefore, in the field of TFT-LCD technology, it is quite important to develop a novel TFT structure greatly increasing W/L without sacrificing the aperture ratio or even increasing the aperture ratio.